Light emitting element and method for manufacturing the same

ABSTRACT

In order to provide a light emitting device and an electronic equipment which suppress luminance deterioration, and have long life, the invention does not form an organic compound layer which is composed of a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer and so on, and electrodes in vacuum-through, as in a conventional vacuum deposition method, but after a hole injection layer, which comprises phthalocyanine, is formed, it is exposed to gas atmosphere. In particular, copper phthalocyanine is exposed to oxygen atmosphere. By this method, provided is an organic light emitting element which has long life, and by using the above-described organic light emitting element, a light emitting device and an electronic equipment are fabricated.

TECHNICAL FIELD

This invention relates to a manufacturing method of a light emittingelement which can obtain fluorescence or phosphorescence, by applying anelectric field to such an element that a film including an organiccompound (hereinafter, inscribed as “organic compound layer”), isdisposed between a pair of electrodes.

BACKGROUND OF THE INVENTION

A light emitting element is a element which emits light by applying anelectric field. As to its light emission mechanism, it is said that byapplying a voltage to electrodes, and interposing an organic compoundlayer therebetween, electrons which are injected from a cathode andholes which are injected from an anode, are recombined at a lightemission center in an organic compound layer to form molecules which arein an excitation state (hereinafter, inscribed as “molecular exciter”),and the molecular exciter discharges energy to emit light on theoccasion of returning to a ground state.

As types of molecular exciters that are organic compound form, a singletexcitation state and a triplet excitation state are possible, and inthis specification, included are both cases in which either excitationstate contributes to light emission.

In such light emitting element, normally, an organic compound layer isformed by a thin film with the thickness even less than 1 μm. Also,since the light emitting element is an element of a self-light emissiontype in which the organic compound layer itself emits light, there isalso no necessity of a back light as used in a conventional liquidcrystal display. Therefore, it is a big advantage that it is possible tofabricate a light emitting element of extremely a thin shape andlightness in weight.

Also, for example, in an organic compound layer of approximately 100–200nm, time from carrier injection until recombination is approximatelytens of nano seconds, considering carrier mobility of the organiccompound layer. Light emission is realized with time within a microsecond order, even if a process from recombination of carrier untillight emission is included. Therefore, it is also one feature that aresponse speed is very fast.

Further, since the light emitting element is a light emitting element ofa carrier injection type, driving by a direct-current voltage ispossible, and generation of noise is reduced. With regard to a drivevoltage, firstly, the organic compound layer is made to be a uniformultra thin film with a thickness of approximately 100 nm. An electrodematerial is selected which lessens a carrier injection barrier to theorganic compound layer, and furthermore, a single heterostructure (2layer structure) is introduced, and thereby, achieved sufficientluminance of 100 cd/m² at 5.5V. (See C. W. Tang et al., Applied PhysicsLetters, Vol. 51, No. 12, 913–915 (1987)).

From characteristics such as a thin shape and lightness in weight/highspeed response/direct-current low voltage drive etc., the light emittingelement is noticed as a next-generation flat panel display element.Also, since it is of a self-light emission type and a viewing fieldangle is wide, its visibility is relatively good, and it is consideredto be effective as a element which can be used for a display screen of aportable equipment.

In the meantime, as a big problem of such light emitting element,reliability of an element is pointed out. Among reliability, inparticular, deterioration over time of luminance is significant, and bigimprovement is necessary.

The deterioration over time of luminance is considered to be basically aphenomenon derived from a material which is used, but it is possible tolengthen a half-life period of luminance by a element structure and adriving method. For example, there is such an example that, as a holeinjection layer, copper phthalocyanine (hereinafter, inscribed as“CuPc”) is inserted, and further, drive is carried out by an alternatecurrent (constant current in case of forward bias, and constant voltagein case of reverse bias) of a rectangular wave but not by a directcurrent, the half-life period of luminance was largely improved. (See S.A. Van Slyke et al., Applied Physics Letters, Vol. 69, No. 15, 2160–2162(1996)).

In Van Slyke et al., lengthening a luminance half-life period up to 4000hours at initial luminance 510 cd/m² was successfully attained. As itscause, cited are elimination of accumulation of space electrification byalternate-current drive, goodness of heat resistance ofN,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidene (hereinafter,inscribed as “NPB”) which is a hole transport layer, and that CuPc,which is a hole injection layer, has an excellent hole injectionproperty.

Also, if surface treatment is applied to indium-tin-oxide (hereinafter,inscribed as “ITO”) which is used for an anode, a contact angle withwater becomes almost 0°. A contact angle of NPB with water isapproximately 70°–80°, and it is understandable that a difference ofsurface energies between ITO and NPB is very large. On this account,when a film of NPB is formed directly on ITO, NPB is easilycrystallized, and deteriorated faster as an element. Inserting CuPc intoa boundary face of ITO and NPB as a hole injection layer to suppresscrystallization of NPB is also a cause which lengthened reliability.

As described above, by using CuPc for a hole injection layer,reliability of a light emitting element is improved, but it cannot besaid that reliability is sufficient. As one of its reasons, it ispointed out that a film forming property is bad, and it is hard toprepare a uniform thin film.

SUMMARY OF THE INVENTION

In this connection, the problem addressed by the invention issuppressing deterioration of luminance over time and lengthening anelement life in a light emitting element which used phthalocyanines, forinstance, CuPc, for a hole injection layer.

Also, a problem addressed is in providing a light emitting device withexcellent endurance by using a light emitting element that the inventiondiscloses. Further, a problem addressed is in providing an electronicequipment with excellent endurance, by using the such a light emittingdevice.

The invention is, in a manufacturing method of a light emitting elementwhich has an anode, a cathode, a light emitting layer which is disposedbetween the anode and the cathode, and a hole injection layer which isdisposed between the anode and the cathode, characterized in that thehole injection layer is formed by phthalocyanine such as CuPc, and afterfilm formation of the hole injection layer, it is exposed to gasatmosphere.

By exposing the hole injection layer which used phthalocyanine tospecific gas atmosphere after film formation, it is possible to obtainhigher reliability than an element which is fabricated by a conventionalvacuum-through film forming method. This inventor considers that it maybe true that film quality of phthalocyanine is improved by being exposedto gas atmosphere so that reliability is heightened.

Also, the invention is a light emitting element which is characterizedby including an electron acceptable compound as a dopant having such anature that it is capable of oxidizing phthalocyanine in the holeinjection layer. By using the hole injection layer in which the electronacceptable compound is doped, lowering of a drive voltage of an elementbecomes possible.

Also in the invention, it is preferable that electron acceptable gassuch as oxygen is used as the above-described gas. By exposing the holeinjection layer to electron acceptable gas atmosphere, lowering of adrive voltage of an element becomes possible.

Also, the invention is, in a light emitting element which has at leastan anode, a cathode, a light emitting layer which is disposed betweenthe anode and the cathode, and a hole injection layer which is disposedbetween the anode and the cathode. The above-described hole injectionlayer is formed by phthalocyanine, and a light emitting device includesthe light emitting element fabricated through a process of exposing togas atmosphere after film formation of the hole injection layer. Also,the invention is characterized in that an electronic device includes thelight emitting device.

By carrying out the invention, it is possible to fabricate a lightemitting element which alleviates deterioration of luminance. Also, byusing the such improved light emitting element, it is possible toprovide a light emitting device in which deterioration of luminance issmall. Further, by fabricating an electronic equipment by using theabove-described light emitting device, it is possible to provide anelectronic equipment which lasts for a longer time than in the priorart.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a manufacturing device which is used tofabricate a light emitting element of the invention.

FIG. 2 is a view showing a structure of a light emitting element.

FIG. 3 is a view showing results of an embodiment 2 and a comparativeexample 1.

FIG. 4 is a view showing results of an embodiment 3 and a comparativeexample 2.

FIG. 5 is a view showing a structure of a light emitting device.

FIG. 6 is a view showing a structure of a light emitting device.

FIG. 7 is a view showing an example of an electronic equipment.

FIG. 8 is a view showing an example of an electronic equipment.

DETAILED DESCRIPTION

Hereinafter, a mode for carrying out the invention will be described indetail with reference to the drawings. As to a light emitting element,it is sufficient that at least one of a first electrode and a secondelectrode is transparent, in order to take out light emission.Generally, in such an element structure, a transparent first electrode(anode) is formed over a substrate, and light is taken out from thefirst electrode (anode). In fact, applicable are such a structure that afirst electrode is inversely made to be a cathode and light is taken outfrom the cathode, and such a structure that light is taken out from anopposite side to the substrate.

Speaking about a light emitting element which is applicable to theinvention, anything may be used if there are at least a light emittinglayer and a hole injection layer which used phthalocyanine, between thefirst electrode and the second electrode. Also as to a light emissioncolor, anything may be used. In case of fabricating a full-color displayelement, and so on, a method of combining light's three primary colors(blue, red, green), a method of combining a color filter with a whitecolor light emitting element, a method of combining a color conversionlayer with a blue color light emitting element, and so on, have beenknown.

Also, the hole injection layer may be such a film in whichphthalocyanine is used as a host and to which electron acceptablecompound (e.g., TCNQ-F4 and V₂O₅ etc.) having such a nature capable ofoxidizing phthalocyanine is doped. A light emitting element using a holeinjection layer in which an electron acceptable compound is doped, sincea drive voltage is low, it is possible to take out light emission at alower voltage, which is useful. Also, since such a fact that a drivevoltage is low means it is possible to reduce a stress which is appliedto an element, it is possible to further expect an advantage of lifeimprovement, by combination with the invention.

In the hole injection layer in which the electron acceptable compound isdoped, hole mobility is heightened, and it becomes possible to make afilm of a light emitting element thicker. By realizing a thicker film,it becomes hard to short-circuit, and it is expected that a yield ratioat the time of making a element becomes better. However, CuPc has such anature that it is easily crystallized when it is made as a thick film.As described above, if improvement of reliability by exposing to gasatmosphere is caused by such a fact that film quality becomes better, weare of the thought that it may be true that crystallization issuppressed by expose to oxygen atmosphere even if CuPc is made as athick film.

Next, speaking about gas to which a substrate is exposed after a holdinjection layer is formed as a film, electron acceptable gas such asoxygen is preferable. The reason is that it is possible to expectlowering of a drive voltage in the same manner as the above-describeddopant.

A light emitting device may be fabricated by using a light emittingelement of the invention. As the light emitting device, there arevarious applications such as illumination by utilizing a simple sheetshaped light emission, and a display device in which pixels are disposedin a matrix shape.

[Embodiment 1]

In this embodiment, a process of making a light emitting element inaccordance with the invention is disclosed, and a manufacturing deviceof a multi-chamber system which is used is described. This manufacturingdevice can carry out sealing processing by uniting with an opposingsubstrate, which is cast in separately from a substrate, after thesubstrate is cast in, and processing of film formation etc. is carriedout continuously.

A light emitting element manufacturing device shown in FIG. 1 has atransport chamber 101 (a substrate and an opposing substrate, atransport robot 110 for transporting a metal mask are attached), asubstrate/mask stock chamber 102 which is coupled to the transportchamber through a gate valve, a preprocessing chamber 103, an organicdeposition chamber 1 104, an organic deposition chamber 2 105, a metaldeposition chamber 106, a CVD chamber 107, a sealing glass stock chamber108, and a sealing chamber 109.

In the first place, cast-in of a substrate and a metal mask fordeposition is carried out in the substrate/mask stock chamber 102. Thesubstrate/mask stock chamber is made to be of an elevator structure (inthis embodiment, assumed to be of 11 stages). Each stage of the elevatorstructure is made to be a dual purpose of a substrate (in thisembodiment, assumed to be of 126.6 mm×126.6 mm) or a mask. It ispossible to accommodate maximum 10 sheets in total for both of thesubstrate and the mask. Since a remaining 1 stage is made to be asubstrate heating state for heading the substrate, it is made to be anempty stage at the time of cast-in. In this manufacturing device, adirection of the substrate is always face-down.

Next, cast-in of the opposing substrate is carried out in the sealingglass stock chamber 108. The sealing glass stock chamber is made to beof an elevator structure (in this embodiment, assumed to be 10 stages).Each stage accommodates maximum 10 sheets of opposing substrate (in thisembodiment, assumed to be of 126.6 mm×126.6 mm) for which preprocessing(representatively, point to drying agent pasting for absorbing moistureinside and outside a panel, and seal agent application for gluingtogether with the substrate) is finished. In this manufacturing device,a direction of the opposing substrate is always face-up.

In this manufacturing device, to all substrates which are cast in, filmforming processing is finished in advance. This is called as a“deposition mode”. After this deposition mode is finished, it is enteredinto a “sealing mode” in which gluing together with the opposingsubstrate is carried out.

Hereinafter, taking a case of using 7 sheets of substrates and 3 sheetsof masks as an example, the deposition mode will be described.

Firstly, it is assumed that the transport chamber 101, the preprocessingchamber 103, the organic deposition chamber 104, the organic depositionchamber 105, the metal deposition chamber 106, and the CVD chamber 107have been exhausted in high vacuum up to 10⁻⁵10⁻⁶ Pa in advance. Duringa period of the deposition mode, the transport chamber is always held inhigh vacuum. Also, it is assumed that deposition materials, which areset in the organic deposition chamber 104 and the organic depositionchamber 105, have been pre-heated at 30° C. lower temperature than eachdeposition start temperature to each material. Preferably, this pre-heattime is 12 hours or more, and it aims to remove moisture which isattached to the deposition material. Next, after exhausting thesubstrate/mask stock chamber 102, a mask is transported to the organicdeposition chamber, the organic deposition chamber, and the metaldeposition chamber. In this manufacturing device, these three are filmforming chambers which use a mask. When the above-described preparationis completed, the substrate is transported to the preprocessing chamber.In the preprocessing chamber, substrate heating in vacuum by a lampheater, and plasma processing by use of a gas system (e.g., O2 plasmaprocessing) are possible, and either processing is carried out to anentire surface of the substrate.

With regard to substrate heating, since it is possible to carry out alsoin the stage of substrate heating in the substrate/mask stock chamber102, it may be carried out here in order to realize throughputimprovement. In this embodiment, it is assumed that substrate heating invacuum by a lamp heater is carried out in the substrate/mask stockchamber after exhaustion. That is, the substrate is transported from thesubstrate/mask stock chamber through the transport chamber 101 to thesubstrate heating stage of the substrate/mask stock chamber, and heaterheating is carried out for 30 minutes at substrate actual temperature150° C. After finishing the heating, the substrate heating stage is heldoff from the lamp heater, and thereby substrate cooling is carried outfor 30 minutes. After finishing the heating, the substrate is carriedthrough the transport chamber to the preprocessing chamber 103, andcooling is carried out (i.e., held in standby in the preprocessingchamber). Thus, it becomes possible to vacuum-heat a next substrate inthe substrate/mask stock chamber also during a period of cooling thesubstrate, which is useful for throughput improvement.

Next, the substrate is transported from the preprocessing chamber 103through the transport chamber 101 to the organic deposition chamber 105.After alignment processing, which used a mask and two units of CCDcameras is finished, a hole injection layer CuPc is formed by 20 nm,with a rate of 0.1 nm/sec. In the organic deposition chamber, a materialis evaporated from a fixed deposition source (in this embodiment,assumed to be six places), and a film is formed on the upper substrate.The substrate is rotated during a period of deposition. In this manner,an in-plane distribution of a film thickness which is formed on thesubstrate is improved. Also, by a co-deposition method in which aplurality of materials are evaporated simultaneously from a plurality ofdeposition sources, it is possible to form a layer in which a substance,which becomes a guest, is doped in a substance which becomes a host.

Next, the substrate is transported through the transport chamber 101 tothe CVD chamber 107. Until such time that the substrate is transportedto the CVD chamber, the CVD chamber is exhausted in high vacuum up to10⁻⁵10⁻⁶ Pa. After the transportation, oxygen gas of high purity issupplied to the CVD chamber at 500 sccm. Also during a period ofsupplying oxygen gas, the CVD chamber is exhausted by a turbo boosterpump, and therefore, pressure in the CVD chamber is constant. After thesubstrate is exposed in slight pressured oxygen atmosphere for 5minutes, supply of oxygen gas is stopped, and the CVD chamber isexhausted in high vacuum.

In the CVD chamber 107, it is possible to form a CVD film on an entiresurface of the substrate. A plasma processing may be carried out using aplurality types of gases. By utilizing this, for example, a siliconnitride film may be formed on a cathode Al as a protective film, and aspreprocessing to the substrate, plasma processing which used a pluralitytypes of gases (e.g., Ar+O₂ plasma processing) may be carried out.

Next, the substrate is transported again to the organic depositionchamber 105 through the transport chamber 101. After finishing thealignment processing, a hole transport layer NPB is formed by 60 nm at0.2 nm/sec.

Next, the substrate is transported to the organic deposition chamber 104through the transport chamber 101. Except for such a fact that thenumber of deposition sources is eight places, other mechanisms and afilm forming processing method are completely the same as those in theorganic deposition chamber 105. Here, a tris(8-quinolinol)aluminumcomplex (hereinafter, inscribed as “Alq3”), which is used as both of alight emitting layer and an electron transport layer, is formed as afilm of 75 nm at 0.1 nm/sec. In particular, in a light emitting layerwhich is formed in the first half period of film formation, its filmthickness is 37.5 nm, and dimethyl-quinacridone (hereinafter, inscribedas “DMQA”) is doped with a slight amount, approximately 0.3 wt %, by theco-deposition method. By this doping, panel life in a finished panel isimproved to a large extent. Also, switching from a light emitting layerto an electron transport layer is carried out smoothly by simply closinga deposition source shutter which is attached to a DMQA depositionsource.

Next, the substrate is transported to the metal deposition chamber 106through the transport chamber 101. Here, as a cathode, CaF₂ is formed asa film of 1 nm at 0.1 nm/sec, and Al is formed as a film of 200 nm at 1nm/sec. In the metal deposition chamber, film formation is possible by aresistance heating (RE) method (there exist 12 points in total of 6point type X 2 as a RE deposition source) and an EB method (there exist6 points in total of 6 point type X 1 as an EB deposition source).However, but considering damage to TFTs on the substrate, use of theresistance heating method is desirable. Mechanisms other than thedeposition source and a film forming method are completely the same asthose in the organic deposition chamber 104 and the organic depositionchamber 105.

The substrate, for which necessary processing is finished as describedabove, is returned again to the substrate/mask stock chamber 102 whichis a point of departure, through the transport chamber 101. Theforegoing showed a series of processing necessary for obtaining a singlecolor panel of green color light emission, but is of non-limiting inparticular.

When the similar processing is completed to all substrates which arecast in, and masks are collected from each deposition chambers to thesubstrate/mask stock chamber 102, the deposition mode is finished, andthis manufacturing device enters into the sealing mode continuously.

The foregoing describes only a case of “mask exchange absence mode” inwhich three masks to be used are disposed in the deposition chamber inadvance and are not exchanged during a period of deposition processing.But according to an element structure, such a request that a pluralityof masks are intended to be used per one chamber of the depositionchamber comes out as a matter of course. Even in such a case, thismanufacturing device is applicable, and it is sufficient that threesheets or more of necessary masks have been set in the substrate/maskstock chamber in advance, and mask exchange is carried out in aninterval of processing in the deposition chamber. On a specification,this mode is called as “mask exchange presence mode” and isdistinguished. In this regard, however, as masks used are increased, thenumber of substrates which can be flowed simultaneously is decreased asa matter of course.

Hereinafter, the sealing mode will be described.

Firstly, there is a necessity to vent the transport chamber 101, thesubstrate/mask stock chamber 102, and the sealing glass stock chamber108. With regard to the transport chamber and the substrate/mask stockchamber, right after finishing the deposition mode, vent processing maybe carried out. Also, with regard to the sealing glass stock chamber, bycarrying out setting of an opposing substrate for which preprocessing isfinished (preferably right before sealing), it is possible to suppressdeterioration of a seal agent and a dry agent. After the setting, bycarrying out exhaustion and vent processing of the sealing glass stockchamber a plurality of times (in this embodiment assumed to be twotimes), it is possible not only to prevent lowering of moisture densityin the transport chamber at the time of the sealing mode, but also tocarry out defoaming of the seal agent which is applied to the opposingsubstrate. It is ideal to carry out the sealing processing right afterfinishing the final vent processing of the sealing glass stock chamber.This is enabled by such a fact that a worker sets successfully timing ofeach processing of vent processing of the transport chamber and thesubstrate/mask stock chamber, cast-in of the opposing substrate into thesealing glass stock chamber, and further, vent processing of the sealingglass stock chamber.

Next, the substrate is transported from the substrate/mask stock chamber102, and the opposing substrate is transported from the sealing glassstock chamber 108, to the sealing chamber 109, respectively, through thetransport chamber 101, respectively. In the sealing chamber, after endparts of the substrates are brought together and mecha-alignmentprocessing of the substrate/opposing substrate is finished, thesubstrate/opposing substrate are glued together, and pressed, andthereby, sealing is carried out. Further, UV irradiation is carried outfrom an opposing substrate side (lower side), and a seal agent (in thisembodiment, assumed to be UV cured resin) is cured. On this occasion, itis possible to selectively apply the UV irradiation only to a portion ofthe seal agent, by using a light shielding mask. In this embodiment, thelight shielding mask is such a thing that a Cr film is formed overquartz glass, and it is impossible to transport it by a transport robotin the transport chamber. Therefore, it is assumed that a worker carriesout the setting directly in the sealing chamber.

By the sealing processing described above, the substrate and theopposing substrate become an integrated panel. This panel is transportedfrom the sealing chamber 109 through the transport chamber 101 to thesubstrate/mask stock chamber 102. Hereinafter, with regard to a nextsubstrate and an opposing substrate, similar processing is carried out.Finally, seven sheets of panels are accommodated into the substrate/maskstock chamber, and the sealing mode is finished. After finishing thesealing mode, a finished panel may be taken out from the substrate/maskstock chamber.

It is possible to carry out a series of processing in the depositionmode and the sealing mode, which is shown above, in a full automaticmanner, by utilizing a control system. Concretely speaking, if a recipe,which included information of a transport route/processing content etc.,has been registered in advance with respect to each substrate, a seriesof processing to each substrate is carried out automatically inaccordance with this registered recipe by simply sending a sign ofprocessing start.

[Embodiment 2]

In this embodiment, in the light emitting element which was fabricatedby the processes shown in the embodiment 1, luminance deterioration wasmeasured on the occasion that constant current drive was carried out.

An element structure is shown in FIG. 2. Firstly, after CuPc as a holeinjection layer 202 was deposited by 20 nm in vacuum of 10⁻⁵–10⁻⁶ Pa, toa glass substrate 207 on which a film of ITO of 110 nm was formed as ananode 201, it is exposed for 5 minutes in oxygen gas atmosphere. Afterthat, as a hole transport layer 203, NPB was deposited by 60 nm. As alight emitting layer 204, a co-deposition film of Alq and DMQA wasdeposited by 37.5 nm. As an electron transport layer 205, Alq wasdeposited by 37.5 mm. Then, as a cathode 206, CaF₂ and Al were depositedby 1 nm and 200 nm, respectively. A mass ratio of Alq and DMQA was1:0.003. Then, it is glued together with an opposing glass with a dryagent, to which ultraviolet cured resin was applied, and ultraviolet raywas applied, and thereby, sealing was carried out.

By using this element, constant current reliability was carried out atcurrent density 9.2 mA/m² which corresponds to 1000 cd/m². A result isshown in a plot “oxygen atmosphere presence” of FIG. 3.

COMPARATIVE EXAMPLE 1

For comparison, in an element which is of the similar element structureto the embodiment 2 and on which NPB was deposited in vacuum-throughwithout being exposed to oxygen atmosphere after CuPc was deposited,initial luminance is set to be the same 1000 cd/m² as the embodiment 2,and a reliability test was carried out on the occasion that constantcurrent drive was carried out (current density 10.2 mA/m²). A result isshown in a plot “oxygen atmosphere absence” of FIG. 3. Comparing bothsides, it is understandable that in an element of “oxygen atmospherepresence”, initial deterioration is particularly suppressed in constantcurrent drive.

[Embodiment 3]

In this embodiment, by slightly changing an element structure of theembodiment 2, constant current reliability of an element was measured.In the embodiment 2, a mass ratio of a light emitting layer is 1:0.003between Alq and DMQA, whereas in this embodiment, it is made to be1:0.01. Other element structures and an element manufacturing methodwere identical. Initial luminance was 1000 cd/m². Current density whichcorresponds to this was 13.4 mA/cm². It is shown in “oxygen atmospherepresence”.

COMPARATIVE EXAMPLE 2

For comparison, in an element which is of the similar element structureto the embodiment 3 and on which NPB was deposited in vacuum-throughwithout being exposed to oxygen atmosphere after CuPc was deposited,initial luminance is set to be the same 1000 cd/m² as the embodiment 3,and a reliability test was carried out on the occasion that constantcurrent drive was carried out (current density 15.9 mA/m²). A result isshown in a plot “oxygen atmosphere absence” of FIG. 4. Comparing bothsides, it is understandable that in an element of “oxygen atmospherepresence”, initial deterioration is particularly suppressed in constantcurrent drive.

[Embodiment 4]

In this embodiment, as an example of a light emitting device which isdisclosed in the invention, a passive matrix type light emitting deviceis illustrated. In FIG. 5A, its top view is shown, and in FIG. 5B, across sectional view at the time of cutting with A–A′ is shown. As anelement of a light emitting element, various modes are possible, and forexample, a structure as in the embodiment 2 and the embodiment 3 in thisspecification may be applicable.

In FIG. 5A, numeral 501 designates a substrate, and a glass material isused. It is possible to use a plastic material, and it is possible touse such a thing that polyimide, polyamide, acrylic resin, epoxy resin,polyether-sulfone (hereinafter, inscribed as “PSE”), polycarbonate(hereinafter, inscribed as “PC”, polyethylene terephthalate(hereinafter, inscribed as “PET”) or polyether nitryl (hereinafter,inscribed as “PEN”) which is made to be of a plate shape, or of a filmshape may be the plastic material.

Numeral 502 designates a scanning line (anode) which is composed of anoxide conductive film, and in this embodiment, ITO is used. Also,numeral 503 designates a data line (cathode) which is composed of ametal film, and in this embodiment, CaF₂ and Al are laminated. Also, 504designates a bank which is composed of acrylic resin, and functions as apartition wall for dividing the data lines 503. As to both of thescanning line 502 and the data line 503, a plurality of them are formedin a stripe shape, and disposed so as to be orthogonal to one another.Although it is not shown in FIG. 5A, an organic compound layer issandwiched between the scanning line 502 and the data line 503, and anintersection part 505 becomes a pixel.

The scanning line 502 and the data line 503 are connected to an externaldrive circuit through a TAB tape 507. Numeral 508 represents a group ofwiring which is composed of the scanning lines 502 which are gatheredtogether, and numeral 509 represents a group of wiring which is composedof aggregation of connection wirings 506 which are connected to the datalines 503. Also, although it is not shown in the figure, in lieu of theTAB tape 507, a TCP that IC is disposed on a TAB tape may be connected.

Also, in FIG. 5B, numeral 510 designates a seal member, and numeral 511designates a cover member which is glued to the substrate 501 by theseal member 510. As the seal member 510, light cured resin may be used,and such a material that degasification is few, and hygroscopicity islow is desirable. As the cover member, the same material as thesubstrate 501 is preferable, and it is possible to use glass (includingquartz glass) or plastic. Here, a glass material is used.

Next, an enlarged view of a structure of a pixel area is shown in FIG.5C. Numeral 513 designates an organic compound layer. As shown in FIG.5C, the bank 504 is made to be of such a shape that a width of a lowerlayer is narrower than a width of a upper layer, and can physicallydivide the data lines 503. Also, a pixel portion 514, which issurrounded by the seal member 510, is made to be of such a structurethat it is shielded from outside air by a sealing member 515 which iscomposed of resin, and prevents deterioration of an organic compoundlayer.

A light emitting device of the invention which is composed of astructure as described above can be fabricated by a very simple process,since the pixel portion 514 is formed by the scanning line 502, the dataline 503, the bank 504 and the organic compound layer 513.

Also, a polarization plate 512 may be disposed over a display surface(surface for observing an image) of the light emitting device which isshown in this embodiment. This polarization plate has an advantage forsuppressing reflection of light which is incident from outside, and forpreventing an observer from being reflected on the display surface. Ingeneral, a circular polarization plate is used. In this regard, however,in order to prevent light which is emitted from the organic compoundlayer from being reflected by the polarization plate to be returned toinside, it is preferable to make a structure in which internalreflection is few by adjusting a refraction index.

[Embodiment 5]

In this embodiment, a light emitting device which has an electric fieldlight emitting element of the invention at a pixel portion, will bedescribed by use of FIGS. 6A, 6B. FIG. 6A is a top view showing thelight emitting device, and FIG. 6B is a cross sectional view cuttingFIG. 6A with B–B′. Numeral 601 shown by a dotted line designates a drivecircuit part (source side drive circuit), numeral 602 designates a pixelportion, and numeral 603 designates a drive circuit part (gate sidedrive circuit). Also, numeral 604 designates a sealing substrate, andnumeral 605 designates a seal agent, and an inside 607 which issurrounded by the seal agent 605 becomes a space.

Numeral 608 designates a wiring for transferring a signal to be inputtedto the source side drive circuit 601 and the gate side drive circuit603, and receives a video signal, a clock signal, a start signal, areset signal and so on from FPC 609 which becomes an external inputterminal. Here, only FPC is shown in the figure, but a printed wiringboard (hereinafter, inscribed as “PWB”) may be attached to this FPC. Itis assumed that the light emitting device in this specification includesnot only a light emitting device main body, but also such a state thatFPC or PWB is attached to it.

Next, a cross-section structure will be described by use of FIG. 6B.Over a substrate 610, a drive circuit part and a pixel portion areformed, and there, the source side drive circuit 601, which is the drivecircuit part, and the pixel portion 602 are shown.

In the source side drive circuit 601, a CMOS circuit is formed in whicha n-channel type TFT 623 and a p-channel type TFT 624 are combined.Also, the TFT which forms the drive circuit may be formed by a publiclyknown CMOS circuit, PMOS circuit, or NMOS circuit. Also shown in thisembodiment is a driver integration type in which a drive circuit isformed over a substrate. However, there is no such necessitynecessarily, and it can be formed outside, not over a substrate.

Also, the pixel portion 602 is formed by a plurality of pixels whichinclude a switching TFT 611, a current control TFT 612, and a firstelectrode 613 which is electrically connected to its drain. An insulator614 is formed so as to cover an end part of the first electrode 613.Here, it is formed by using a positive type photosensitive acrylic resinfilm.

Also, in order to make coverage better, a curved surface havingcurvature is formed on a upper end part or a lower end part of theinsulator 614. For example, in case that positive type photosensitiveacrylic is used as a material of the insulator 614, it is preferable tomake only the upper end part of the insulator 614 hold a curved surfacehaving curvature radius (0.2 μm–3 μm). Also, as the insulator 614, it ispossible to use each of a negative type which is photosensitive andbecomes infusible to etchant by light, or a positive type which becomesfusible to etchant by light.

On the first electrode 613, an electric field light emitting layer 616,and a second electrode 617 are formed, respectively. Here, as a materialwhich is used for the first electrode 613 which functions as an anode,it is desirable to use such a material that a work function is large.For example, besides a single layer film such as an ITO film, an indiumzinc oxide film, a titanium nitride film, a chromium film, a tungstenfilm, a Zn film, and a Pt film, it is also possible to use a laminationlayer of titanium nitride and a film which includes aluminum as a majorcomponent, and a three layer structure of a titanium nitride film, afilm which includes aluminum as a major component and a titanium nitridefilm, and so on. If a lamination layer structure is used, wiringresistance is low, and good ohmic contact is obtained, it is possible tohave it functioned as an anode.

Also, the organic compound layer 616 may use anything if there are atleast a light emitting layer and a hole injection layer which usedphthalocyanine. For example, a structure as in the embodiment 2 and theembodiment 3 in this specification may be applicable.

Further, as a material which is used for the second electrode (cathode)617 which is formed on the organic compound layer 616, a material thathas a small work function (Al, Ag, Li, Ca, or these alloys MgAg, MgIn,AlLi, CaF₂, or CaN) may be used. In case that light, which is generatedin the electric field light emitting layer 616, passes through thesecond electrode 617, it is fine to use a lamination layer of a metalthin film whose film thickness is reduced, and a transparent conductivefilm (ITO, indium oxide zinc oxide alloy, zinc oxide etc.) as the secondelectrode (cathode) 617.

Further, it is made to be of such a structure that a light emittingelement 618 is provided in a space 607 which is surrounded by theelement substrate 601, the sealing substrate 604, and the seal agent605, by gluing the sealing substrate 614 together with the elementsubstrate 610 by the seal agent 605. Besides such a case that the space607 is filled with inert gas (nitrogen, argon, etc.), such a structurethat it is filled with the seal agent 605 is to be included.

It is preferable to use epoxy series resin for the seal agent 605. Also,it is desirable that these materials be a material which does nottransmit moisture and oxygen as much as possible. Also, as a materialwhich is used for the sealing substrate 604, it is possible to use aplastic substrate which comprises polyimide, polyamide, acrylic resin,epoxy resin, PES, PC, PET, PEN, and so on, besides a glass substrate anda quartz substrate.

As described above, it is possible to obtain a light emitting devicewhich has an electric field light emitting element of the invention.

[Embodiment 6]

The light emitting device of the invention, which is described in theabove-identified embodiment, has an advantage in that life is long.Therefore, an electronic equipment in which the above-described lightemitting device is included as a display part etc. becomes an electronicequipment which lasts for a longer time than in the prior art.

Also, since the above-described light emitting device is of a self-lightemission type, there is no necessity of a back light as in a liquidcrystal display device. Since a thickness of the organic compound layeris less than 1 μm, it is possible to realize thin shape and lightness inweight. Therefore, an electronic equipment in which the above-describedlight emitting device is included as a display part etc. becomes anelectronic equipment which is of a thinner shape and lighter in weightthan in the prior art. This is also extremely useful since it isdirectly linked to convenience (lightness and compactness on theoccasion of carrying about), with regard to an electronic equipment suchas, in particular, a portable equipment. Further, also in an entirety ofelectronic equipment, it is beyond question that to be of a thin shape(not to take up much space) is useful in view of a transport aspect(mass transport is possible), and an installation aspect (securement ofa space such as a room etc.).

Since the above-described light emitting device is of a self-lightemission type, it has such characteristics that it excels in visibilityin a bright place as compared to a liquid crystal display device, and inaddition, a viewing field angle is wider. Therefore, there is a bigadvantage also as to a point of easily viewable display in an electronicequipment which has the above-described light emitting device as adisplay part.

That is, an electronic equipment which used a light emitting device ofthe invention, in addition to advantages of a conventional lightemitting element such as thin shape and lightness in weight/highvisibility, also has a feature of long life, and is extremely useful.

In this embodiment, an electronic equipment which includes a lightemitting device of the invention as a display part is illustrated as anexample. Applicable examples are shown in FIGS. 7A–7F and FIGS. 8A, 8B.For a light emitting device which is included in an electronic equipmentof this embodiment, each of the light emitting device which aredisclosed in the invention may be used. For example, the display devicewhich is shown in the embodiment 4 and the embodiment 5 may be used.

FIG. 7A shows a display device which used a light emitting element, andincludes a housing 701 a, a support table 702 a and a display part 703a. By fabricating a display which used a light emitting device of theinvention as the display part 703, it is possible to realize a displaywhich is thin and light in weight, and lasts for a long time. Thus,transport becomes simple, and small space on the occasion ofinstallation becomes possible. In addition, usable life is also long.

FIG. 7B shows a video camera which includes a main body 701 b, a displaypart 702 b, a sound input part 703 b, an operation switch 704 b, abattery 705 b, and an image receiving part 706 b. By fabricating a videocamera which uses a light emitting device of the invention as thedisplay part 702 b, it is possible to realize a video camera which is oflong life and weight is reduced.

FIG. 7C shows a digital camera which includes a main body 701 c, adisplay part 702 c, an eye piece 703 c, and an operation switch 704 c.By fabricating a digital camera which used a light emitting device ofthe invention as the display part 703 c, it is possible to realize adigital camera which has long life, and is light in weight.

FIG. 7D shows an image reproducing device which is equipped with arecording medium, and includes a main body 701 d, a recording medium(CD, LD, or DVD etc.) 702 d, an operation switch 703 d, a displaypart(A) 704 d, and a display part(B) 705 d. The display part(A) 704 dmainly displays image information, and the display part(B) 705 d mainlydisplays textual information. By fabricating the above-described imagereproducing device which used a light emitting device of the inventionas these display part(A) 704 d and the display part(B) 705 d, it ispossible to realize the above-described image reproducing device whichlasts for a long time and is light in weight. In this image reproducingdevice which is equipped with the recording medium, a CD reproducingdevice, a game equipment and so on are included.

FIG. 7E shows a portable type (mobile) computer which includes a mainbody 701 e, a display part 702 e, an image receiving part 703 e, anoperation switch 704 e, and a memory slot 705 e. By fabricating aportable type computer which used a light emitting device of theinvention as the display part 702 e, it is possible to realize aportable type computer which has long life, and is of a thin shape andlight in weight. This portable type computer can record and reproduceinformation in such a recording medium as a flash memory and anintegrated non-volatile memory.

FIG. 7F shows a personal computer which includes a main body 701 f, ahousing 702 f, a display part 703 f, and a keyboard 704 f. Byfabricating a personal computer which uses a light emitting device ofthe invention as the display part 703 f, it is possible to realize apersonal computer which has long life, is of a thin shape, and is lightin weight. In particular, in case that application to a mobile equipmentis necessary as in a notebook personal computer, a point of lightnessbecomes a big advantage.

The above-described electronic equipment have been receiving manyopportunities for displaying information which is distributed through anelectronic communication line such as Internet and wirelesscommunication such as electromagnetic waves, and in particular, anopportunity for displaying moving image information has been increased.A response speed of a light emitting element made in accordance with thepresent invention is very fast, and is suitable for the such movingimage display.

Next, FIG. 8A shows a portable telephone which includes a main body 801a, a sound output part 802 a, a sound input part 803 a, a display part804 a, an operation switch 805 a, and an antenna 806 a. By fabricating aportable telephone which uses a light emitting device of the inventionas the display part 804 a, it is possible to realize a portabletelephone which has long life, is of a thin shape, and is light inweight.

FIG. 8B shows an audio equipment (for example, in-car audio), andincludes a main body 801 b, a display part 802 b, and an operationswitches 803 b, 804 b. By fabricating an audio equipment which uses alight emitting device of the invention as the display part 802 b, it ispossible to realize an audio equipment which has long life, and is lightin weight. Also, in this embodiment, an in-car audio is shown as anexample. However, the present invention may be used for a home use audioequipment as well.

In the electronic equipment as shown in FIG. 7A–FIG. 8B, by furtherembedding a light sensor, and by disposing means for detectingbrightness of use environment, it is useful to provide a function sothat light emission luminance is modulated in accordance with brightnessof use environment. If it is possible to secure brightness of 100–150 bya contrast ratio as compared to brightness of use environment, a usercan recognize an image or textual information without problems. That is,it becomes possible to make it easily viewable by increasing luminanceof an image in case that use environment is bright, and to suppresselectric power consumption by suppressing luminance of an image in casethat use environment is dark.

Also, since various electronic equipment which uses a light emittingdevice of the invention as a light source can be made to have long lifeand it is possible to realize a thin shape and reduce its weight, it canbe said that it is very useful. Representatively, it is an electronicequipment which includes a light emitting device of the invention as alight source such as a back light or a front light of a liquid crystaldisplay device, or as a light source of a lighting equipment.

Therefore, in using liquid crystal displays for all of the display partsof the electronic equipment shown in the embodiments of FIG. 7A–FIG. 8B,and by fabricating an electronic equipment which uses a light emittingdevice of the invention as a back light or a front light of that liquidcrystal display, it is possible to provide electronic equipment whichhas long life, and in addition, which is thin and light in weight.

1. A manufacturing method of a light emitting device comprising ananode, a cathode, a light emitting layer disposed between said anode andsaid cathode, and a hole injection layer disposed between said anode andsaid cathode, the method comprising: forming said hole injection layerthat comprises phthalocyanine; and exposing said hole injection layer tooxygen gas after forming said hole injection layer.
 2. The methodaccording to claim 1, wherein said phthalocyanine is copperphthalocyanine.
 3. The method according to claim 1, wherein an electronacceptable compound capable of oxidizing phthalocyanine is doped in saidhole injection layer.
 4. The method according to claim 3, wherein saidelectron acceptable compound is TCNQ-F4 or V₂O₅.
 5. The method accordingto claim 3, wherein said electron acceptable compound is TCNQ-F4 orV₂O₅.
 6. A manufacturing method of a light emitting device comprising ananode, a cathode, a light emitting layer disposed between said anode andsaid cathode, and a hole injection layer disposed between said anode andsaid cathode, the method comprising: forming said hole injection layerthat comprises phthalocyanine; doping an electron acceptable compoundcapable of oxidizing phthalocyanine into said hole injection layer; andexposing said hole injection layer to oxygen gas after forming said holeinjection layer.
 7. A manufacturing method of a light emitting devicecomprising an anode, a cathode, a light emitting layer disposed betweensaid anode and said cathode, and a hole injection layer disposed betweensaid anode and said cathode, the method comprising: forming said holeinjection layer that comprises phthalocyanine in a first chamber of amulti-chamber system; and exposing said hole injection layer to oxygengas in a second chamber of the multi-chamber system after forming saidhole injection layer, wherein the multi-chamber system has at least thefirst chamber and the second chamber.